1. Field of the Invention
This invention generally relates to cable television (CATV) communication systems. More particularly, the invention relates to a CATV settop terminal which includes a system for enhancing the performance of the RF tuner.
2. Description of the Related Art
The CATV transmission spectrum typically comprises a bandwidth of frequencies up to 1000 MHz. During transmission of signals over the CATV network between the headend and the settop terminals, the higher frequencies experience greater attenuation than the lower frequencies. To compensate for the unequal attenuation, CATV network operators install devices throughout the CATV network to periodically equalize and amplify the signals as they are transmitted over the network. However, once the signal is output from the last active component in the transmission network, such as a line amplifier, no compensation for the unequal attenuation is provided. When line extenders are introduced or when a subscriber is located a long distance from the tap, large inequalities develop between the strength of signals at lower frequencies and those at higher frequencies. This degrades the performance of the RF tuner.
A second problem that reduces the performance of the RF tuner is the introduction of second and higher order distortions caused by the plurality of input carrier frequencies. As CATV network operators offer more channels over their networks, the bandwidth of the CATV network continues to expand. This results in an increase in the number of input carrier frequencies, which further degrades the performance of the RF tuner due to second and higher order distortions.
Accordingly, there exists a need for an inexpensive method to improve RF tuner performance in dual conversion CATV settop terminals.